Light Driven Ultrafast Bioinspired Molecular Motors: Steering and Accelerating Photoisomerization Dynamics of Retinal

Abstract

Photoisomerization of retinal protonated Schiff base in microbial and animal rhodopsins are strikingly ultrafast and highly specific. Both protein environments provide conditions for fine-tuning the photochemistry of their chromophores. Here, by combining time-resolved action absorption spectroscopy and high-level electronic structure theory, we show that similar control can be gained in a synthetically engineered retinal chromophore. By locking the dimethylated retinal Schiff base at the C11C12 double bond in its trans configuration (L-RSB), the excited-state decay is rendered from a slow picosecond to an ultrafast subpicosecond regime in the gas phase. Steric hindrance and pretwisting of L-RSB are found to be important for a significant reduction in the excited-state energy barriers, where isomerization of the locked chromophore proceeds along C9C10 rather than the preferred C11C12 isomerization path. Remarkably, the accelerated excited-state dynamics also becomes steered. We show that L-RSB is capable of unidirectional 360° rotation from all-trans to 9-cis and from 9-cis to all-trans in only two distinct steps induced by consecutive absorption of two 600 nm photons. This opens a way for the rational design of red-light-driven ultrafast molecular rotary motors based on locked retinal chromophores.

Rhodopsins: An Excitingly Versatile Protein Species for Research, Development and Creative Engineering

“…With the rapidly growing insight in the structural and mechanistic potential of the rhodopsin pigments, this is expected to change at short notice. So far, electro-optical phenomena have been investigated in 2D crystals, lipid films and other matrices ( Oesterhelt et al, 1991 ; Miyasaka et al, 1992 ; Hong, 1994 ; Wagner et al, 2013 ; Zhao et al, 2015 ; Ji et al, 2017 ; Gruber et al, 2022 ). With help of the above mentioned software packages, the design of specific constructs with high performance and stability under the system’s conditions will be facilitated.…”

Cryogenic Fluorescence Spectroscopy of Ionic Fluorones in Gaseous and Condensed Phases: New Light on Their Intrinsic Photophysics

“…The occurrence of torsional dynamics is important in a broad range of other systems, including chromophores in photoactive proteins, , light-driven molecular machines, and photoswitch molecules used in technology, such as photopharmacology. These dynamics are often difficult to discern directly in a single experiment.…”

CO‐Preserving Photoinduced Transfer of Cymantrenyl Moiety: a Tandem Experimental and Computational Investigation

“…Absorbing light, a molecule reaches an electronically excited state which may have drastically different distribution of electrons (wavefunction) leading to qualitatively different chemical behavior compared to the ground state. These phenomena may be quantitively described by means of ground‐state and excited‐state potential‐energy hypersurface topology [2–7] . In some cases, use of photochemical steps significantly shortens synthetic routes, allowing transformation of simple substrates into complex, polycyclic, or highly functionalized compounds [8,9] .…”

“…These phenomena may be quantitively described by means of ground-state and excitedstate potential-energy hypersurface topology. [2][3][4][5][6][7] In some cases, use of photochemical steps significantly shortens synthetic routes, allowing transformation of simple substrates into complex, polycyclic, or highly functionalized compounds. [8,9] New product families or libraries difficult to achieve with ground-state reactions are thus available, opening new per-spectives in the search of biologically active compounds or catalytic agents.…”